opAssign and classes

[BCS]

Bill Baxter wrote:
> I wrote a class with an opAssign.
> But I find I keep getting bitten by this:
> 
>     MyType x = value;
> 
> When I should be typing:
> 
>     MyType x = new MyType;
>     x = value;
> 
> Somehow I just keep forgetting to do that.
> Then I get a nice nondescript "Error: Access violation" at some unknown 
> point in my program that I have to track down.
> 
> Anyone else find themselves making this kind of error?
> Any thoughts for how I or the compiler could help protect against this 
> kind of mistake?
> 

1> convert a seg-v to an exception (signal ??)
2> implement poor man's stack tracing:

T fn()
{
	debug scope(failure) writef(__FILE__":"~itoa!(__LINE__));
	...
}

> I thought I could stick a check for 'this is null' in the opAssign 
> method but that doesn't help because apparently it's dereferencing the 
> null pointer to look up opAssign's address that causes the Error, not 
> what happens in the call itself.
> 
> --bb